1. Field of the Invention
This invention concerns improvements in and relating to processing, particularly, but not exclusively to the processing of nuclear fuel materials.
2. Present State of the Art
The production of fuel grade nuclear fuel from mined uranium ore is a long and complex process. Many variations in the process are known but in general terms the process involves taking the ex-mine grade material and gradually converting and enriching it until it is in. a form and of a grade suitable for producing fuel pellets. Stages in this process are the concentration of the initial uranium oxides as uranyl nitrate hexahydrate; a de-nitration stage to convert the material into UO.sub.3 ; a reduction stage to convert the UO.sub.3 to U.sub.2 ; a hydrofluorination stage to form UF.sub.4 ; a further fluorination stage to produce UF.sub.6 ; an enrichment procedure by physical or chemical means; and the conversion of UF.sup.6 in its enriched form to ceramic grade UO.sub.2 which is in a suitable form to be formed into fuel pellets.
Substantial processing plants, in terms of their size, capital investment and running costs, are necessary to perform all of these stages. Transportation between the various stages with its attendant problems are encountered. In addition, the fluorination technique in particular requires a complex and hazardous electrolysis process to produce the fluorine required.
Recycling of fuel similarly involves a series of complex chemical and physical steps to separate the various fission products from the depleted fuel and to upgrade the .sup.235 U concentration in the material to a stage where once again it can be employed as fuel.
The complexities of these processes are also present in other processing lines in the fuel cycle, in relation to thorium, plutonium and other materials for instance.